For most people, when we think of gravity, we think of things like, weight, and pulling down. Though gravity does pull down, there is a misconception that gravity is what causes our weight on whatever surface, which is wrong. We actually perceive weight through the normal force.
The normal force is perpendicular to whatever surface an object is in contact with(if you’re in mid air there is no normal force). Gravity pulls down, normal force pushes up, hence a surface supporting our weight. Another point is Newton’s 3rd law: for every reaction(gravity), there must be an equal and opposite reaction(normal force). If there was no normal force to support our weight, we would fall through the ground until we reached the Earth's center of mass.
So then why are the astronauts not literally falling toward the Earth? To successfully orbit the earth, you have to have the right velocity. If the velocity is too low, gravity will over power that velocity and pull you down to Earth. If the velocity is just right, there will be an equilibrium between the velocity and Earth’s gravity. The minimum orbit velocity for Earth is 17,000 mph.
Another question one may find themselves asking about this concept is, can you only be in space to feel weightless? No! In order to feel weightless, there needs to be an absence of normal force, and you need to be in a free fall. At the fair, there are rides that bring you up really high then drop you. When you are in free fall, you are accelerating at -9.8 meters per second squared (acceleration of gravity). Whenever gravity is the only force acting upon you, you will feel weightless. Another example is in Apollo 13 the movie. The weightless space scenes were filmed in a free falling plane with only gravity pulling down. Once again, since gravity was the only force acting on them, they experienced weightlessness.